1. Field of the Invention
The present embodiments relate generally to laser systems and more particularly to wavelength beam combining systems and methods.
2. Description of the Prior Art
Wavelength beam combining (WBC) is a method for scaling the output power and brightness from laser diode bars, stacks of diode bars, as well as other lasers arranged in one or two-dimensional array.
WBC methods have been developed to combine beams along the slow dimension of each emitter as well as the fast dimension of each emitter. See for example, U.S. Pat. Nos. 6,192,062, 6,208,679 and 2010/0110556 A1. In prior patents, U.S. Pat. Nos. 6,192,062 and 6,208,679, beam combining is performed along the array dimension. As such, the external cavity is more sensitive to imperfections in the laser elements. Furthermore, when broad-area laser elements are used the spectral utilization is poor. In prior art 2010/0110556 A1 beam combining is performed along the stacking dimension. In such implementations the external-cavity is much less sensitive to imperfections in laser elements. Furthermore, since beam combining is performed along the stacking dimension or near diffraction-limited dimension spectral utilization is high. However, one of the main drawbacks of this implementation is the output beam quality is limited to the beam quality of a single beam combining element or a single bar. Typical COTS bars have 19 to 49 emitters. A typical 19-emitter bar can only couple into 200 μm/0.22 NA fiber or at best 100 μm/0.22 NA fiber. The brightness of such a system is barely adequate for some applications like industrial laser cutting of thin and thick sheet metal, including stainless steel, mild steel, aluminum, and copper. Diode laser bars with a lower number of emitters are desired for better output beam quality. However, they are less readily available at a much higher cost per unit of output power as compared with standard diode laser bars. Within the prior art these individual emitters are assumed to be pre-aligned or fixed in position and as such, the output beam profile generated from combining across one of these dimensions is a result of this pre-alignment or fixed positioning of the array of emitters. This application addresses manipulating individual, one-dimensional, two-dimensional, as well as randomly placed emitters into a preferred alignment conducive to generating a preferred output beam profile. The result is more robust, and much higher spatial brightness can be obtained using COTS diode laser bars and stacks with a large number of laser elements (19 to 49 per bar or higher). Additional benefits will become apparent in the detailed description of the application.
The following application seeks to solve the problems stated.